A senior intelligence official said "several different sources" had placed
Mohammed at the Hamburg apartment that was used for meetings by three of the Arabs who are
believed to have piloted the hijacked planes, as well as by several others implicated in
planning and funding the operation.

The new intelligence may help to solve one of the major puzzles about Sept. 11who
outside the hijacking teams helped coordinate their actions and provided the link to
senior Al Qaeda leaders. Mohammed is now believed to have filled at least part of that
pivotal role.

The intelligence official said interrogation of Al Qaeda prisoners captured in Afghanistan
and elsewhere, as well as "tracing of documents" and other raw intelligence
collected in recent months, indicated that Mohammed was one of the few people with direct
knowledge of the recruiting, training, funding and other operational details behind the
attacks.

"The number of people central to this plan was very small," said the official,
who spoke on condition of anonymity. "He was one of them."

Although Mohammed was little known to the public until this week, officials said he has
now been tied to the 1993 bombing of the World Trade Center, a foiled 1995 attempt to bomb
12 U.S. airliners over the Pacific, the 1998 bombings of U.S. embassies in Tanzania and
Kenya, and the Sept. 11 attacks on New York and the Washington area.

"He is the Forrest Gump of Al Qaeda," a Bush administration official said.
"He has more of a presence in some of their plots than we had previously known."

The official said counter-terrorism experts had focused their attention over the last two
years chiefly on the more high-profile Abu Zubeida, the Al Qaeda operations chief who was
captured in March in Pakistan.

"Khalid Shaikh Mohammed had been quiet and had stayed off the airwaves," the
official added. "In hindsight, I don't think people appreciated how important a
player he had become in the Al Qaeda hierarchy. We are learning all that now."

Mohammed was indicted by a U.S. court in 1996 for his alleged role in the airliner plot,
but the federal arrest warrant was sealed so he wouldn't know that authorities were
scouring the globe for him.

Officials said it is still unclear precisely when Mohammed visited Hamburg, or which of
the hijackers he met there. Mohamed Atta, Marwan al-Shehhi and Ziad Jarrahwho are
believed to have piloted three of the hijacked planeslived in the northern German
city for most of 1999.

Atta's two roommatesRamzi bin al-Shibh and Said Bahajialso are suspected of
participating in the plot. Unable to get a U.S. visa, Bin al-Shibh helped wire tens of
thousands of dollars to the hijackers and to Zacarias Moussaoui, who was arrested before
Sept. 11 and later was charged with conspiracy. Investigators have said Moussaoui was
supposed to take bin al-Shibh's place as the 20th hijacker.

Mohammed's whereabouts are unknown, although officials hinted that at least one
unsuccessful covert operation was launched to capture him in the late 1990s in the Middle
East.

"We don't have a real good bead on where's he been," another intelligence
official said. "Obviously we'd love to talk to him."

U.S. authorities are offering a reward of as much as $25 million for information leading
to his capture. He is believed to be in Afghanistan or Pakistan.

Mohammed initially was known as an accomplice to Ramzi Yousef, the convicted mastermind of
the first World Trade Center bombing in 1993 and of a 1995 plot to detonate bombs aboard
12 U.S. airliners over the Pacific Ocean.

According to the 1996 U.S. indictment, Yousef, using the name Dr. Adel Sabah, rented an
apartment in the Tiffany Mansion condominium building in the San Juan section of Manila,
the capital of the Philippines, in August 1994.

In the next two months, Yousef and Mohammed lived there and used the location to mix
chemicals for explosives. They were also in possession of "modified timing
devices," the indictment said.

On Dec. 1, 1994, they and a number of other men blew up an explosive device at Manila's
Greenbelt Theater. That was a test, authorities say, for the explosive device placed on
Philippine Airlines Flight 434 from Manila to Tokyo 10 days later. The small bomb exploded
in midair, according to the indictment, killing passenger Haruki Ikegami.

The plot was uncovered in January 1995 when Mohammed's "bomb factory" caught
fire and authorities searching Yousef's computer found detailed plans to blow up the
airliners. Abdul Hakim Murad, a commercial pilot who wanted to hijack planes, and Wali
Khan Amin Shah, a suspected Bin Laden associate, were captured and convicted in the plot
along with Yousef.

Also in the computer: a communication signed by "Khalid Shaikh" and an
apparently related letter that threatened to attack American targets "in response to
the financial, political and military assistance given to the Jewish state in the occupied
land of Palestine by the American Government."

The letter, apparently written by Mohammed and his associates, also threatened to
assassinate the president of the Philippines, attack aircraft or even launch a biochemical
attack if one of their co-conspirators was not released from custody.

At the time, U.S. counter-terrorism officials tried but failed to find connections between
the group and the still-embryonic terrorist network called Al Qaeda.

They concluded, however, that Mohammed was unlike the low-level "soldiers" who
had helped Yousef in the airliner plot, which was called Bojinka, Bosnian for "big
noise."

Mohammed, they said, appeared to be an equal to Yousef, and someone whom Yousef trusted
and respected, said one former law enforcement official involved in that investigation and
prosecution.

"Yousef was a one-man band who planned it, built [the explosives], and it never would
have happened without him," said the official, who spoke on the condition of
anonymity. "The others were a bunch of clowns who couldn't have done it without
Yousef."

Except Mohammed, the official said. "He was someone of stature that Yousef
respected," said the former official. He also said Mohammed was believed to be
Yousef's relative by marriage.

But Mohammed now appears to have had early links to the larger terror network. His
citizenship remains in questionthe FBI says he is from Kuwait, while other officials
suspect he may be from Baluchistan, a Pakistani province. Moreover, he has had access to
significant sums of money, an indication that others may be backing him, officials said.

"I was always under the impression that he had connections; he could move around, had
money and could go from one place to another," said the former official.

Later, authorities linked Mohammed to the 1998 bombings of the two U.S. embassies in
Africa. On Wednesday, they said his role in those attacks was still being investigated.

Since Sept. 11, authorities have struggled to piece together the complex plot, as well as
the Al Qaeda hierarchy and network that spawned it. They now have concluded that Mohammed
had quietly risen from a low-level figure to a position of relative authority.

He had access to Zubeida and Bin Laden, and authorities now believe that he thought up the
Sept. 11 plot, possibly incorporating elements of the first World Trade Center attack and
the botched airliner plot.

"He's definitely a player," said the Bush administration official Wednesday.
"He's definitely a major guy. People have known about him for a while."

The latest information places him in Hamburg in 1999, after the Sept. 11 cell had been
assembled.

The young Arabs who formed it had arrived in Germany over the previous decade, but all
were in Hamburg and were in contact with one another by 1998.

Atta came first, arriving as a student in 1992 from his home in Egypt. In early 1999, he
moved out of student housing and into a refurbished apartment on Marienstrasse that
investigators think served as the base for the cell.

Al-Shehhi moved to Germany from the United Arab Emirates in 1996, settling two years later
in a Hamburg apartment close to Atta's. Jarrah arrived in the fall of 1997.

German investigators think that the Hamburg group was chosen by Al Qaeda for their
technical skills and relative sophistication. The investigators say the three probably
were singled out at Al Qaeda training camps in Afghanistan, probably in late 1998 or early
1999.

In any case, German federal police say airline records show that the three presumed
pilots, plus Bin al-Shibh, flew to Pakistan in late 1999, presumably en route to
Afghanistan. The three pilots were in Florida by July 2000, the first leg of the U.S.
travel that ultimately would end in the airborne attacks.

Times staff writer Terry McDermott in Los Angeles contributed to this report.